US put North Korea on notice it won't tolerate any provocation, while Pyongyang threatened a nuclear strike in response.
Military force cannot resolve tension over North Korea, China said on Thursday, while an influential Chinese newspaper urged the North to halt its nuclear programme in exchange for Chinese protection.
With a US aircraft carrier group steaming to the area and tension rising, South Korea said it believed the United States would consult it before any preemptive strike against the North.
Fears have been growing that the reclusive North could soon conduct its sixth nuclear test or more missile launches in defiance of UN sanctions and stark warnings from the United States that a policy of patience was over.
China, North Korea's sole major ally and benefactor, which nevertheless opposes its weapons programme, has called for talks leading to a peaceful resolution and the denuclearisation of the Korean peninsula.
"Military force cannot resolve the issue," Chinese Foreign Minister Wang Yi told reporters in Beijing. "Amid challenge there is opportunity. Amid tensions we will also find a kind of opportunity to return to talks."
While US President Donald Trump has put North Korea on notice that he would not tolerate any provocation, US officials have said his administration was focusing its strategy on tougher economic sanctions.
Trump has, however, diverted the USS Carl Vinson aircraft carrier group towards the Korean peninsula, which could take more than a week to arrive.
Wang warned that history would hold any instigator to account.
"Whoever provokes the situation, whoever continues to make trouble in this place, they will have to assume historical responsibility," Wang said.
South Korean Foreign Minister Yun Byung-se told parliament in Seoul he believed Washington would consult Seoul if it was considering a preemptive strike. The United States has about 28,500 troops in South Korea.
A Washington-based think-tank that monitors North Korea, 38 North, said satellite images on Wednesday showed activity around the North's Punggye-ri nuclear test site on the east coast that indicated it was ready for a new test.
South Korean officials said there were no new signs to indicate a test was more likely, although they also said the North appeared ready to conduct a test at any time.
An influential state-backed Chinese newspaper said the best option for North Korea and its leader, Kim Jong-un, was to give up its nuclear programme, and China would protect it if it did.
"As soon as North Korea complies with China's declared advice and suspends nuclear activities ... China will actively work to protect the security of a denuclearised North Korean nation and regime," said an editorial in the Global Times, which is published by the Communist party's People's Daily.
Japanese Prime Minister Shinzo Abe underscored fears about threats from North Korea, telling parliament in Tokyo that Pyongyang could have the capacity to deliver missiles equipped with sarin nerve gas.
A senior Japanese diplomat said the United States was putting "maximum pressure" on North Korea to resolve issues peacefully, while putting responsibility on China to sway its old ally.
"We will watch what action China takes," the diplomat said.
While Japan did not see a high risk of military action, it expected to be consulted by the United States if it decided to attack. North Korea has about 350 missiles that can hit Japan.
On Tuesday, North Korea warned of a nuclear attack on the United States at any sign of American aggression. The North is technically at war with the United States and South Korea after the 1950-53 Korean War ended in a truce and not a peace treaty.
The North regularly threatens to destroy both countries.
Trump and Chinese President Xi Jinping spoke by telephone on Wednesday, just days after they met in the United States for the first time, underscoring the sense of urgency about North Korea.
Trump said on Twitter his call with Xi was a "very good" discussion of the "menace of North Korea". He said later on Wednesday the United States was prepared to tackle the crisis without China, if necessary.
Aljazeera | Source: Reuters news agency – Photo: Sailors conduct flight operations on the aircraft carrier USS Carl Vinson on April 8 [Matt Brown/US Navy via AP]